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31.12.06 - Non-GMO approach for the improvement of heavy metal accumulation and extraction of high yielding crop species for efficent phytoextraction of contaminated soil. Thesis EPFL, n° 3414 (2005). Dir.: Prof. J.-P. Schwitzguebel.

The PhD thesis of Mrs Erika Nehnevajova reports on an original, innovative and important research, developed simultaneously in the field and at laboratory scale, to remediate soils contaminated by metals, by the use of appropriate and efficient green plants. .

Non-GMO approach for the improvement of heavy metal accumulation and extraction of high yielding crop species for efficent phytoextraction of contaminated soil.

Since most of the metal hyperaccumulating wild plants only produce very low biomass and many high yielding crops accumulate only moderate amounts of metals, the current research is mainly focused on the overcoming of these limitations and the optimization of metal phytoextraction. The main goal of the present study was the improvement of metal accumulation and extraction properties of Helianthus annuus L by chemical mutagenesis (non-GMO approach). Sunflowers, hybrid cultivar Salut and inbred lines were treated with chemical mutagen ethyl methanesulfonate (EMS).

The effect of chemical mutagenesis on metal accumulation and extraction of new sunflower M1 and M2 mutants was directly assessed on a metal contaminated field in Rafz (Switzerland). The sunflower mutants of M2 generation showed a 2-3 times higher metal shoot accumulation than the control plants, and even considerably enhanced metal extraction. The best M2 sunflower "giant mutant" 14/185/04 showed an increased metal extraction: 7.5 times for Cd, 9.2 times for Zn and 8.2 times for Pb compared to the control plants.

Theoretical calculations of phytoextraction potential of new sunflower variants point out that the best sunflower mutant can produce up to 26 t dry matter yield per ha and remove 13.3 kg Zn per ha and year at the sewage sludge contaminated site of Rafz; that is a gain factor of 9 compared to Zn removal of sunflower controls. Furthermore, the use of sunflower oil and biomass for technical purposes (lubricants, biogas, biodiesel) should produce an additional value and improve the economical balance of phytoextraction.

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